Most, if not all, modern, diagnostic imaging units, such as ultrasound, magnetic resonance imaging, x-ray computed tomography, etc. have display monitors on which the user directly views the images produced by the system. The display monitors usually have a combination of brightness and either contrast or "Picture" controls so that the user may set the display parameters to their taste and to allow the user to compensate for different room lighting levels. Imaging sessions may be conducted at various levels of room illumination ranging from darkness to fully illuminated rooms.
Most, if not all, modern, diagnostic imaging systems employ recording devices that take either digital data or analog video as their input and produce hardcopy and/or digitally archived records of the images displayed on the display monitor. The media of hardcopy can be thermal paper, X-ray film, transparencies, 35 mm film, Polaroid film, color dye transfer prints and various other media. Some imaging systems employ digital archiving apparatus in lieu of or in addition to hardcopy recording devices. Images recorded on digital archiving apparatus are typically later displayed on monitors other than the scanning system's display monitor and can also be used to produce a hardcopy. Most hardcopy devices have contrast and brightness (or combined "picture") controls, whereas digital archiving systems have a fixed input requiring precompensation. Some of them have exposure or intensity/saturation controls as well. Most hardcopy devices require a non-linear "Gamma" mapping function to be applied to match or compensate for the particular non-linear response characteristics of the recording unit and the recording media; gamma being generally an expression of the relationship between exposure and resultant image density in the range between minimum and maximum image density. The user, of course, expects the recorded images (or later displayed images from a digital archiving system) to match the initially displayed/viewed image very closely in brightness and contrast. However, the user adjusts the display monitor parameters to compensate for ambient lighting conditions and personal taste without readjusting or compensating the recording devices, so there is little potential for the recorded image to match the independently adjusted displayed image. Note, as used herein, the term recorder includes one or both of a hardcopy display device or a digital picture archiving apparatus.
It is, of course, desirable to match the brightness, contrast and intensity/saturation of the hardcopy image to that of the displayed image as closely as possible. Furthermore, the image matching should exist over the range of adjustment of the display monitor parameters without a continuing need for manually readjusting and compensating the recording device(s) for every ambient light situation or for each user.
It is therefore an object of the present invention to provide a display system and method in which hardcopy or digitally archived record output is comparable (within the limits of the recording device and media) to that which is displayed/viewed on display monitors of the system. It is a further object to provide a diagnostic imaging system in which the hardcopy or digitally archived image is automatically adjusted to yield images comparable to images displayed on the system's display monitor throughout their range of adjustment.